The present application relates to the protection of electrical machines used in electrical power systems.
In power generation, transmission, and distribution systems, it is important that electrical devices operate with a high level of reliability even in the presence of unanticipated events. However, for some of these events it is desirable to protect a piece of equipment from being damaged and for these instances reliability of a power generation, transmission, and distribution system is sacrificed momentarily. For example, a generator may be tripped (and consequently be removed from service) due to various reasons, including faults internal to the generator and certain disturbances in a transmission and distribution network. When electrical devices in power generation, transmission, and distribution systems are switched out in order to protect these devices, at least a portion of the power system will not operate optimally.
To protect electrical devices in power generation, transmission, and distribution systems, protection devices, such as protection relays, are placed in communication with devices that are to be protected, such that voltage levels, current levels, etc. can be monitored and reacted to accordingly. More particularly, the electrical protection device is often programmed with one or more protection functions that enable the protection device to protect against particular faults, such as pole slipping, underimpedance, and other suitable faults. Parameters of the protection functions are typically set as a function of the electrical device that is to be protected, its immediate power-system surroundings, the past experiences of an operator that is setting the parameters, and the custom or practices of a given utility.
While use of protection devices has aided in reducing damage to electrical devices, several problems remain. For example, setting parameters of protection functions in protection devices is sometimes referred to as an inexact science, and parameters may be incorrectly set due to factors such as incomplete or incorrect information, inadvertence, or the like. Additionally, parameters that are initially correct may, over time, become incorrect as a result of aging of the electrical device, changes or refurbishment of electrical devices, or changes to the associated electrical power system. If parameters of a protection function are improperly set, more frequent or unwarranted tripping of an electrical device may occur. Further, if faults are not properly detected by a protection device, damage to an electrical device that is to be protected (or a portion of a transmission and distribution network) may occur.